1. Field of the Invention
The present invention relates to fabricating color screens, and, more particularly, to fabricating ultra-high resolution three-color screens.
2. Description of Related Art
Phosphor screens for high density television (HDTV) cathode ray tubes (CRTs) are currently made having a triad pitch of the order of 0.75 to 1.0 mm (750 to 1,000 .mu.m). As used herein, the phrase "triad pitch" refers to the distance across the three phosphor colors, including any separation between the phosphors, to the beginning of the next set of phosphors. The triad geometry may be either lines, dots, or any other configuration capable of being generated by conventional mask-making techniques. Phosphor screens for use in computer terminals have a minimum triad pitch of approximately 0.28 mm (280 .mu.m). Such phosphor screens are considered state-of-the-art at present.
The cathode ray tubes are built in sizes ranging from approximately 10 inch diagonal to super-large tubes of the order of 36 inch diagonal. The larger tubes will have larger triad pitches and make up for that by the large diameter (or diagonal) of the display area, so that the overall horizontal and vertical resolutions are the same between small and large diameter tubes. The electron guns must complement the screen resolution.
Future color tubes for use in "Heads Up" displays (HUD) for aircraft cockpits require very high resolution in a very small tube. Tube diameters are of the order of one inch (2.54 cm) maximum. In order to achieve resolution in these tubes approaching that of the larger tubes mentioned above, it is necessary to greatly increase the resolution capability of the screens. Instead of dealing with triad pitches of the order of 0.28 mm (280 .mu.m), screens must be fabricated with triad pitches of the order of 150 .mu.m and less. Naturally, the source of electrons to bombard the triads and produce cathodoluminescence must also be capable of producing a complementary resolution. Additionally, the advent of new designs in flat panel displays offer the possibility of improved resolution in these devices if higher resolution screens were available. For example, the development of field emission flat panels can make microscopically small, sharp point emitters with conventional microelectronic processing. The very fine spacing of these emitters can make use of the higher resolution color screens described herein. The same situation exists in electroluminescent flat panels and plasma panel displays, where the screen addressing circuitry, fabricated by microelectronic methods, vastly outperforms the conventional present day screen resolution capability. The situation requires a drastic change in the technology of making color screens.
Thus, there is a need to fabricate phosphor color screens with triad pitches of 150 .mu.m and less.